Use of water-external micellar dispersions in oil recovery



lit

23 Claims ABSTRACT OF THE DISCLOSURE Secondary-type crude oil recovery is effected by injecting into a subterranean formation 1-20% formation pore volume of a water-external micellar dispersion of hydrocarbon and surfactant dispersed in water and moving it through the formation to displace crude oil therefrom.

BACKGROUND OF THE INVENTION United States Patent No. 3,266,570 to Gogarty teaches a flooding process using an oil-external soluble oil followed by a water-external emulsion. Gogarty teaches that the back portion of the water-external emulsion improves the miscibility with a subsequent water drive.

United States Patents Nos. 3,330,344 and 3,348,611 to Reisberg teach flooding with an aqueous solution containing swollen micelles of a surfactant and an amphiphilic polar organic compound. Reisberg teaches that these solutions will solubilize the crude oil in sand packs. Suitable amphiphilic organic compounds include higher molecular weight monohydroxy aliphatic and alicyclic alcohols containing six or more carbon atoms.

Applicant has discovered that a water external micellar dispersion comprised of water, hydrocarbon and surfactant is useful in secondary type recovery processes (especially tertiary recovery) to recover crude oil from subterranean formations. Preferably, the micellar dispersion contains a semi-polar compound and optionally an electrolyte. The injection of about 1 to about 20% formation pore volume of the micellar dispersion provides eflicient recovery of crude oil from a subterranean formation. The micellar dispersion can be followed by a mobility buffer, one purpose of which is to protect the dispersion from invasion of a subsequent water drive.

DESCRIPTION OF INVENTION This invention is applicable to crude oil recovery processes where artificial means facilitate removal of the oil. More specifically, the invention is applicable to secondary oil recovery and to tertiary recovery processes in subterranean formations which have been reduced to residual oil saturation.

The term micellar dispersion as used herein is meant to include micellar solutions, water-external microemulsions [Schulman and Montague, Annals of the New York Academy of Sciences, 92, pages 336-37l (1961)], transparent emulsions and micellar dispersion technology taught by C. G. Sumner, Claytons, The Theory of Emulsions and Their Technical Treatment, 5th edition, pp. 315-320 (1954). Micellar dispersions differ from emulsions in many ways, the strongest differentiation being that the former are thermodynamically stable whereas the latter are not.

The micellar dispersions of this invention are waterexternal. That is the hydrocarbon phase is internally dispersed. In an oil-external micellar dispersion the water phase is internally dispersed.

The micellar dispersion is composed essentially of hydrocarbon, an aqueous medium, surfactant suflicient tent O Patented Apr. 14, 1970 ICC to impart thermodynamic stability to the solution, semipolar organic compound and optionally electrolyte. Examples of volume amounts are from 1% to about 50% of hydrocarbon, from about 40% to about aqueous medium, at least about 4% surfactant, from about 0.01% to about 5% of semi-polar compound and up to about 4% by weight of electrolyte. In addition, the dispersions and%or subsequent slugs can contain corrosion inhibiting agents, bactericides, etc.

Examples of hydrocarbon include crude oil (both sweet and sour) and partially refined fractions thereof, e.g., side cuts from crude columns, crude column overheads, gas oils, kerosene, heavy naphthas, naphthas, straight-run gasoline, and liquified petroleum gases. Pure hydrocarbons are not desired. Based on economics, the preferred hydrocarbon is one locally available and is crude oil. The unsulfonated hydrocarbon (e.g. heavy vacuum gas oils) in petroleum sulfonates is also useful.

The aqueous medium can be soft, brackish, or a brine. Preferably, the water is soft but it can contain small amounts of salts which are compatible with the ions in the subterranean formations being flooded.

Surfactants useful with the micellar solutions include nonionic, cationic, and anionic surfactants. Examples of such surfactants include sodium glyceryl monolaurate sulfate, dihexyl sodium succinate, hexadecylnaphthalene sulfonate, diethyleneglycol sulfate, glycerol disulfoacetate monomyristate, p-toluidene sulfate laurate, p-chloroaniline sulfate laurate, sodium sulfate oleylethylanilide, triethanolamine myristate, N-methyltaurine oleamide, pentaerythritol monostearate, polyglycerol monolaurate, triethanolamine oleate, morpholine stearate, hexadecyl trimethylammonium chloride, ditetradecyl dimethyl ammonium chloride, n-dodecyl-diethyleneglycol, sulfate, monobutylphenyl phenol sodium sulfate, and triethanolamine laurate or triethanolamine oleate. Other useful surfactants include Duponol WAQE (a 30% active sodium lauryl sulfate marketed by Du Pont Chemical Coporation, Wilmington, Delaware), Energetic W-lOO (a polyoxyethylene alkyl phenol marketed by Armour Chemical Company, Chicago, 111.), Triton X (a polyoxyethylene alkyl phenol marketed by Rohrn & Haas, Philadelphia, Pennsylvania) and Arquad 12-50 (a 50% active dodecyl trimethyl ammonium chloride marketed by Armour Chemical Company, Chicago, 111.).

Preferably, the surfactant is a petroleum sulfonate, also known as alkyl aryl naphthenic sulfonate, and preferably an alkali salt thereof. Examples of preferred surfactants are the sodium and ammonium petroleum sulfonates having an average molecular weight of from about 360 up to about 500, and more preferably from about 420 to about 460. The surfactant can be a mixture of low and high molecular weight sulfonates or a mixture of two or more different surfactants.

The semi-polar organic compound (also known as cosurfactants and co-solubilizers) useful with the invention can have limited water solubility. However, compounds having 0 to infinite water solubility are useful. Preferably, they have limited Water solubility of from about 0.01% to about 20% and more preferably from about 1% to about 5% at ambient temperature. Examples of semipolar compounds include alcohols, amino compounds, esters, aldehydes and ketones containing from 1 up to about 20 or more carbon atoms and more preferably from 3 to about 16 carbon atoms. The semi-polar compound is preferably an alcohol, e.g. isopropanol, nand isobutanol, the amyl alcohols such as n-amyl alcohol, 1- and 2-hexanol, 1- and 2-octanol, decyl alcohols, alkaryl alcohols such as p-nonyl phenol and alcoholic liquors such as fusel oil. Particularly useful alcohols include the primary butanols, primary pentanols and secondary hexanols. Concentrations of from about 0.01% up to about 5 volume percent of the semi-polar compound is useful in the micellar dispersion and more preferably from about 0.2 up to about 3%. Mixtures of two or more semi-polar compounds are useful in the micellar dispersions.

Electrolytes are useful within the water-external micellar dispersions. Examples of such electrolytes include inorganic bases, inorganic acids, inorganic salts, organic bases, organic acids, and organic salts which are strongly or weakly ionized. Preferably, the electrolytes are inorganic bases, inorganic acids and inorganic salts, e.g. sodium hydroxide, sodium chloride, sodium sulfate, hydrochloric acid, sulfuric acid, sodium nitrate, ammonium chloride, ammonium hydroxide, and potassium chloride. Examples of other useful electrolytes can be found in United States Patent No. 3,330,343. The type and concentration of electrolyte will depend on the aqueous medium, surfactant, semi-polar organic compound, hydrocarbon and on the reservoir temperature. The use of acids or neutral salts is preferred with dispersions containing hydrophilic surfactants and high reservoir temperatures. Electrolytes yielding a higher pH, e.g. NaOH are preferred with more oleophilic surfactants.

The mobility of the dispersion should be about equal to or less than the mobility of the combination of the crude oil and formation water within the subterranean formation. Such a mobility is desired to avoid viscous fingering of the micellar dispersion into the formation fluids.

The volurnne of the micellar dispersion useful with this invention is from about 1% to about 20% formation pore volume. Larger percentage pore volumes are useful but may be economically unattractive. More preferably, from about 2% to about 10% formation pore volume is useful and 3% to about 6% formation pore volume gives very efi'lcient results. The micellar dispersion is injected through an injection means into the formation. The injection means includes the well bore including that area contiguous to the oil-bearing rock at the bottom of the well.

The size of the mobility buffer (also identified as the front portion of the drive material) can vary from about up to about 75% formation pore volume and more preferably is within the range of from about 25% to about 60% formation pore volume. However, this formation pore volume can be adjusted to satisfy the requirements of the particular reservoir being flooded. The mobility buffer can have a mobility about equal to or less than the mobility of the micellar dispersion. In addition, from about 5% to about 100% of the mobility buffer can be characterized as having graded mobilities from a low at the front portion of the mobility buffer to a high at the juncture with a subsequent water drive.

After the mobility buffer is injected into the subterranean formation, suflicient water drive is injected to move or displace the water-external micellar dispersion and mobility buffer toward a production means, e.g. production well, in fluid communication with the subterranean reservoir. Crude oil displaced by these injected fluids is recovered at a production well.

The following examples are presented to specifically illustrate working embodiments of the invention. Limitations are not to be implied by these examples. It is intended that all equivalents obvious to those skilled in the art be included within the scope of the invention. Percents are based on volume, unless otherwise specified.

EXAMPLE 1 Fired Berea sandstone cores 4 feet long by 3 inches in diameter having characteristics indicated in Table I are saturated with distilled water containing 18,000 p.p.m. of NaCl, flooded to irreducible water saturation with a crude oil obtained from the Henry lease in Illinois (hereinafter identified as Henry produced crude and having a viscosity of 5.9 cps. 72 F. and a specific gravity of 0.833) and are then flooded to residual oil saturation with water obtained from the Henry lease in Illinois (hereinafter identified as Henry plant water, example of an analysis is 17,210 p.p.m. of total dissolved solids and having a pH of 7.7). The cores are then flooded with the indicated percent pore volumes of a water-external micellar dispersion containing 80.5% of water obtained from the Palestine water reservoir in Palestine, Ill. (hereinafter identified as Palestine water, example of an analysis is 412 p.p.m. of total dissolved solids and having a pH of 7.6-8.0), 8.7% of an ammonium alkyl aryl naphthenic sulfonate (having an average molecular weight of about 440 and containing 78.3 active sulfonate and the residue unsulfonated paraffinic oil), 1.1% of n-amyl alcohol, 0.5% isopropanol, and 9.2% of Henry produced crude. After the micellar dispersion is injected into the cores, there is injected 1.2 pore volumes of thickened water solution (mobility buffer) composed of Palestine water, 1,200 p.p.m. of No. 530 Pusher (a high molecular weight partially hydrolyzed polyacrylamide sold by Dow Chemical Company) and 1% fusel oil. The core characteristics, percent pore volume of micellar dispersion slugs and the results of the flooding tests are indicated in Table I.

TABLE I Percent formation Core Characteristics pore volume of Percent Residual micellar recovery Effective Permeoil dispersion of crude porosity, ability, saturation, injected oil in percent md. percent into core core The fluid recovered from Sample 0 was analyzed and found to contain 32.8% of the ammonium petroleum sulfonate originally incorporated into the micellar dispersion.

EXAMPLE 2 The procedure of Example 1 is repeated except the micellar dispersion is composed of 71% Palestine water, 1.3% n-amyl alcohol, 0.5% isopropanol, 9.9% of ammonium petroleum sulfonate, and 17.3% of Henry produced crude. The core characteristics, percent pore volumes, and percent crude oil recovery results are indicated in Table II:

Fired Berea sandstone cores 4 feet long by 2 inches in diamet r, having characteristics indicated in Table III, are saturated with Henry plant water, flooded to irre ducible water saturation with Henry produced crude, and then waterflooded to residual oil saturation with Henry plant water. The cores are then injected with water-external micellar dispersions composed of 27.41% Henry produced crude, 6.67% of an ammonium petroleum sulfonate (having an average molecular weight of about 450 and composed of about active sulfonate), 64.62% of Palestine water containing 0.98 weight percent of sodium hydroxide, 0.74% of isopropanol, and 0.56% of nonylphenol. The micellar dispersion has a viscosity of 29.5 cps. at 72 F. The micellar dispersion injections are followed with 1.25 pore volumes of a thickened water slug composed of 800 p.p.m. of No. 530 Pusher, 4% of isopropanol, 5O p.p.m. of NH SCN, and 96% of Palestine water.

To show that the water-external systems have comparable recoveries to that of oil-external micellar systems,

6 3.21% of isopropanol, 0.81% of nonyl phenol, 62.66% of Palestine water, and 0.979 weight percent of sodium hydroxide.

Samples G-H 27.42% of Henry crude oil,

6.67% of the above ammonium petroleum sulfonate, 0.74% of isopropanol,

0.56% of nonyl phenol,

64.61% of Palestine water, and

0.979 weight percent of sodium hydroxide.

TABLE III Percent formation Core Characteristics pore Percent volume of recovery Effective Perme- Residual micellar of crude porosity, ability, oil saturadispersion oil in Sample percent md. tlon,percent injected core Water-external systems:

EXAMPLE 4 After the dispersions are injected into the core sam- Fired Berea sandstone cores 4 feet long by 2 inches in diameter having characteristics indicated in Table IV are treated as follows: 1) Samples C, D, and F are first saturated with distilled water containing 16,500 p.p.m. of NaCl, flooded to irreducible Water saturation by using Henry crude oil and flooded to residual oil saturation With distilled water containing 16,500 p.p.m. of NaCl, (2) Samples A, B, E, and G-H are treated as above except they are Waterflooded with Henry plant water. Thereafter, the cores are injected with Table IV indicated percent formation pore volumes of water-external micellar dispersions composed of:

Samples A-B 40.25% of Henry crude oil, 7.43% of an ammonium sulfonate having an average molecular weight of about 450 and being about 80% 4.5

active sulfonate, 0.83% of isopropanol,

Sample B 800 p.p.m. of No 530 Pusher, p.p.m. of NH SCN, 0.08% of isopropanol, and 99.9% of Palestine Water.

Samples A and C-H 800 p.p.m. of No. 530 Pusher, 50 p.p.m. of NH SCN,

4% of isopropanol, and

96% of Palestine Water.

The results of the flooding tests are indicated in Table IV:

0.34% of nonyl phenol,

51.15% of Palestine water, and 1.201 Weight percent of Samples C-F 26.85% Henry crude oil, 6.47% of the above ammonium petroleum sulfonate,

TABLE 1V 2 Percent Core Characteristics pore Percent Percent volume recovery recovery Effective Perme- Residual oil injection of crude of porosity, ability, saturation, of disperoil in sulfonate percent md. percent sion slug core injected EXAMPLE 5 Fired Berea sandstone cores 4 feet long by 2 inches in diameter having characteristics indicated in Table V are saturated with distilled water containing 18,000 p.p.m. of NaCl, flooded with Henry crude oil to irreducible water saturation and then flooded with Henry plant water to residual oil saturation. The cores are then flooded at ambient temperature with indicated percent formation pore volumes of a micellar dispersion having the compositions indicated in Table V:

TABLE V Micellar Dispersion Composition, percent Component Aqueous medium:

(1) Henry plant water (2) Palestine water Surfactant, ammonium petroleum sulfonate having:

(a) Average M.W.=440, 78.3% active sulfonate The core samples are then flooded with 1.2. formation pore volumes of a thickened water solution having the following compositions:

Palestine water containing 1% of n-butanol, and 1200 ppm of No. 530 Pusher.

Results of the flooding tests are indicated in Table VI:

11. The process of claim 10 wherein the mobility buffer has a mobility about equal to or less than that of the micellar dispersion.

12. The process of claim 11 wherein from about 5% up to about 100% of the mobility buffer is characterized as having graded mobilities increasing from front to rear.

13. A process of recovering crude oil from an oilbearing subterranean formation having at least one injection means in fluid communication with at least one production means, comprising:

(1) injecting through the injection means into the formation 1% to abOut 20% formation pore volume This example shows that the hydrocarbon in the crude sulionate (to. the sulfonate contains the indicated percent active sulfonate and the residue is unsulfonated hydrocarbon) will suffice in the micellar dispersions of this invention.

What is claimed is:

1. A process for recovering crude oil from an oil-bearing subterranean formation having at least one injection means in fluid communication with at least one production means, comprising injecting through the injection means into the formation a water-external micellar dispersion comprised of hydrocarbon, an aqueous medium and surfactant and displacing the micellar dispersion toward the production means to recover crude oil therefrom.

2. The process of claim 1 wherein the water-external micellar dispersion contains semi-polar organic compound.

3. The process of claim 1 wherein the water-external micellar dispersion contains electrolyte.

4. The process of claim 1 wherein the micellar dispersion contains at least about 4% by volume of the surfactant.

5. The process of claim 1 wherein the hydrocarbon is crude oil or partially refined fractions of crude oil.

6. The process of claim 1 wherein the surfactant is anionic.

7. The process of claim 1 wherein the hydrocarbon is unsulfonated hydrocarbon in petroleum sulfonate.

8. The process of claim 1 wherein from about 1% to about 20% formation pore volume of the micellar dispersion is injected into the formation.

9. The process of claim 1 wherein the mobility of the micellar dispersion is about equal to or less than the mobility of the formation fluids ahead of the micellar dispersion within the subterranean formation.

10. The process of claim 1 wherein a mobility buffer is injected into the formation after the micellar dispersion is injected therein.

of a water-external micellar dispersion comprised of hydrocarbon dispersed in an aqueous medium, and surfactant and semi-polar organic compound, then (2) injecting a mobility buffer into the formation, the

mobility buffer characterized as having a mobility about equal to or less than that of the formation fluids within the subterranean formation, and

(3) injecting sufficient water drive into the formation to move the micellar dispersion and mobility buffer toward a production means and recovering crude oil therefrom.

14. The process of claim 13 wherein the micellar dispersion contains electrolyte.

15. The process of claim 13 wherein the micellar dispersion has a mobility about equal to or less than that of the formation fluids.

16. The process of claim 13 wherein the mobility buffer is characterized as having an average mobility between that of the micellar dispersion and that of the water drive.

17. The process of claim 13 wherein from about 2% up to about 10% formation pore volume of micellar dispersion is injected into the subterranean formation.

18. The process of claim 13 wherein from about 5% to about 75% formation pore volume of mobility buffer is injected into the formation.

19. The process of claim 13 wherein from about 5% to about of the mobility buffer is characterized as having graded mobilities increasing from front to rear.

20. The process of claim 13 wherein the surfactant within the micellar dispersion is an anionic surfactant.

21. The process of claim 13 wherein the micellar dispersion contains at least about 4% by volume of the surfactant.

22. The process of claim 13 wherein the hydrocarbon 3,297,084 1/1967 Gogarty et al 166-9 is crude oil or partially refined fractions of crude oil. 3,330,344 7/1967 Reisberg 166-9 23. The process of claim 13 wherein the hydrocarbon 3,348,611 10/1967 Reisberg 166--9 is unsulfonated hydrocarbon in petroleum sulfonate. 3,373,809 3/1968 Cooke 166-9 References Cited 5 STEPHEN J. NOVOSAD, Primary Examiner UNITED STATES PATENTS CL 3,261,399 7/1966 Coppel 166-9 166-274 3,266,570 8/1966 Gogarty 166-9 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3, Dated 29 Inventor(s) Stanley C. Jones It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 59: Delete 336-371 and insert Column 2, line 8: Delete 'a:nd%or" and insert --and/ or--.

Column 2, line 38: Delete "coporaltion' and insert corporati on-- Column 3, line 29: Delete "volumne' and insert --volume--.

Column 5, line 69: Delete '51. 15% of Palestine water, and" Column 5, line 70: Delete "1.201 weight percent of sodium hydroxide.

SIGNED A???) SEALED SEAR Attest:

mm: x. sammnm. Edwm nmh Oomissioner or Paton Amuting 

